1. Field of the Invention
The present invention relates to a vacuum control valve that controls a flow of a gas through a vacuum chamber employed in a vacuum apparatus that uses plasma.
2. Description of the Related Art
Manufacture of a semiconductor device includes a process that uses plasma, such as plasma etching, for example. In the plasma etching process, a vacuum pressure in a vacuum chamber is controlled while introducing etching gas through a vacuum control valve. The vacuum pressure control is performed by manipulating a conductance of the vacuum control valve. In a pendulum type vacuum control valve used widely in plasma etching, conductance manipulation is performed by operating a pendulum-type valve body so as to adjust a valve opening, for example, as described in Japanese Patent Application Publication No. 2009-117444. With a method of adjusting the valve opening by operating a pendulum-type valve body, however, controllability is poor in a low flow rate region (a low conductance region), making it impossible to respond to a reduced etching gas flow rate.
A poppet type vacuum control valve, which is capable of responding to a reduced etching gas flow rate, may also be used to control the vacuum pressure. A poppet system is a system of adjusting the conductance by manipulating a distance between the valve body and a valve seat (i.e. a lift) in accordance with a linear motion of a piston, for example, as described in Japanese Patent Application Publication Nos. 2010-276096 and 2003-194257. However, a metallic bellows of a poppet type vacuum control valve is not plasma-resistant, and therefore a poppet type vacuum control valve cannot be employed in a vacuum chamber that uses plasma. The metallic bellows is a constituent component used to seal a sliding part, which is required for the linear motion of the piston, to maintain a degree of vacuum, for example, as described in Japanese Patent Application Publication Nos. 2000-130635 and H3-260072.